The advantage of providing twin walls for tanks, such as fuel storage tanks, by constructing a monitorable interstitial space between the twin walls is understood and a number of systems are available for providing twin walls. Typically, the integrity of the tank is monitored by subjecting the space between the twin walls to a vacuum. If the vacuum fails this indicates that one of the twin walls has become porous, for example through mechanical piercing of one of the walls or through corrosion.
Some examples of solutions to the above-described problem are described below.
The publication WO 00/32394 describes a method of lining a fuel storage tank in which a keying means is applied to the surface of a tank. A corrosion barrier is then applied to the keying means. An interstitial grid is then applied to the tank and pliable glass reinforced plastics materials laid onto the grid. The glass reinforced plastics material is then exposed to ultra violet rays to cure the material and form a hardened inner liner shell for the tank.
An apparatus and method for lining a tank so as provide a monitorable interstitial space is described in GB2444486. This apparatus uses sheet material having adhesive applied to both sides to attach itself and the other components of the lining to the wall of a tank. The apparatus and method described in this invention have been found to be particularly effective in the lining of underground and above-ground storage tanks used for storing fuel, acids and other fluids.
Pipelines are susceptible corrosion. If a pipeline were to become porous the environmental damage resulting could be much worse than that occurring in the case of a leaking in tank, since in the case of a pipeline the volume of fluid is not limited in the same way as it is with a tank.
In some environments it is necessary to insulate pipelines. Corrosion of the outer surface of the pipeline can be a particular problem where pipelines are insulated. This is because condensation occurs on the surface of the pipeline and builds up between the surface thereof and the insulation.
Whilst the apparatus and methods described above in connection with providing monitor able interstitial space for tanks are not limited to tanks, and could theoretically be applied to pipelines, to do so is not straightforward.
In the case of a tank the environment where the work is carried out is self-contained, substantially stable, and controllable. For outdoor pipelines this is not the case and prevailing environmental conditions may either severely limit, or prevent the use of the components of the above-described apparatus and the equipment required for their installation.
It would therefore be desirable to provide an apparatus and method for providing an interstitial space between two walls, one of which may be the wall of a pipe or pipeline.